The invention relates to a seat belt buckle engagement detector for detecting engagement of a buckle and a tongue plate of a seat belt to detect that a passenger wears the seat belt, and a seat belt system for warning non-wearing of the seat belt and controlling a seat belt retraction.
In a vehicle, such as an automobile, while driving, a passenger has an obligation to wear a seat belt. The seat belt includes web portions attached to a seat and to a retractor. When the seat belt is worn, the web retracted in the retractor is pulled out and a tongue plate attached to a forward end thereof is engaged with a buckle fixed to the seat.
A switch, i.e. buckle switch, for detecting engagement of the buckle and the tongue plate is provided in the buckle. When the buckle and the tongue plate are not engaged with each other, a contact point thereof is turned on, and when the buckle and the tongue plate are engaged with each other, the contact point thereof is turned off.
The automobile includes a seat belt system which controls such that when the seat belt is not worn or put on, an engine does not start; the automobile does not run; or the passenger is warned by a sound. Recently, it has been proposed that retraction of the seat belt is carried out by a motor and control thereof is performed by the seat belt system.
FIG. 5 is a schematic view showing a conventional seat belt buckle engagement detector. A power source from a battery 21 is supplied to one end of a seat belt warning lamp 24 through an ignition switch 22 and a fuse 23. The other end of the seat belt warning lamp 24 is grounded through a buckle switch 25. A voltage on a side of the buckle switch of the seat belt warning lamp 24 is inputted into a seat belt system 26. The other display lamps 27 are connected parallel to the seat belt warning lamp 24.
When the ignition switch 22 is turned on, in case the buckle and the tongue plate are not engaged with each other, since the buckle switch 25 is turned on, the seat belt warning lamp 24 is lighted on, and at the same time, a signal of an earth potential is inputted to the seat belt system 26. In case the buckle and the tongue plate are engaged with each other, the buckle switch 25 is turned off, the seat belt warning lamp 24 is turned off, and at the same time, a signal of a potential corresponding to a voltage of the battery 21 is inputted into the seat belt system 26.
As described above, the conventional seat belt buckle engagement detector starts its operation only when the ignition switch 22 is turned on. Therefore, while the ignition switch 22 is turned off, the seat belt warning lamp 24 is held in a light-off state, so that the potential to be inputted to the seat belt system 26 becomes unstable. Therefore, in the seat belt system 26, the input is connected to a positive voltage through a pull-up resistance or is connected to an earth potential through a pull-down resistance to thereby prevent the input signal from being unstable.
In the normal state, in case the ignition switch is not turned on, since the automobile does not run, it seems that there is no necessity for wearing of the seat belt to be detected in this state. However, the automobile may be driven by an outer force, such as hauling. In such a case, even if the ignition switch is not turned on, it is necessary to detect a wearing condition of the seat belt. Also, when a passenger gets on the automobile, it is preferable that the seat belt is worn before the ignition key is turned on.
In view of the above problem, the present invention has been made, and an object of the invention is to provide a seat belt buckle engagement detector, wherein even if an ignition key is not turned on, wearing of a seat belt can be detected to thereby provide a warning sign and carry out other controls.
Further objects and advantages of the invention will be apparent from the following description of the invention.
According to a first aspect of the present invention to attain the above object, a seat belt buckle engagement detector includes a device for detecting engagement of a buckle and a tongue plate of a seat belt even in case an ignition switch of an automobile is turned off.
In the device, even if the ignition switch of the automobile is turned off, since engagement of the buckle and the tongue plate is detected, even in case the automobile is driven by hauling, a warning for wearing a seat belt can be provided. Also, even before a passenger gets on the automobile and turns on the ignition switch, a warning sign for wearing the seat belt can be provided and a seat belt retraction control can be carried out.
According to a second aspect of the invention to attain the above object, in the first aspect, the seat belt buckle engagement detector has a function for turning on or off the device for detecting the engagement of the buckle and the tongue plate even in case the ignition switch of the automobile is turned off by an output of a seat belt system.
In the first aspect, even in case the ignition switch of the automobile is turned off, since there is provided the device for detecting the engagement of the buckle and the tongue plate, under certain circumstances, there may be a case where an electric current of a battery is consumed by a current flowing to the detecting device. However, in the second aspect, the device for detecting the engagement of the buckle and the tongue plate can be turned on or off by the output of the seat belt system even in case the ignition switch of the automobile is turned off. For example, in case a power source of the seat belt system is not turned on, even if the ignition switch of the automobile is turned off, the current of the battery can be prevented from being consumed by turning off the device for detecting the engagement of the buckle and the tongue plate.
Incidentally, the xe2x80x9cseat belt systemxe2x80x9d mentioned in the present specification is a system for carrying out operations relative to the seat belt, such as generating a seat belt wearing warning, retracting the seat belt and controlling the seat belt.
According to a third aspect of the present invention to attain the above object, in the seat belt buckle engagement detector as stated in the first aspect, there is provided a seat belt buckle engagement detector, wherein the device for detecting the engagement of the buckle and the tongue plate has a detecting function even if a warning lamp for showing non-engagement of the buckle and the tongue plate of the seat belt is broken.
In the seat belt buckle engagement detector as shown in FIG. 5 and explained in the prior art section, when the seat belt warning lamp 24 is broken, the seat belt system can not detect that the buckle switch is turned on or off. In the third aspect, however, the device for detecting the engagement of the buckle and the tongue plate does not lose its detecting function even when the warning lamp for showing that the buckle and the tongue plate of the seat belt are not engaged with each other is broken. Even in such a case, the seat belt system can detect the seat belt buckle engagement.
According to a fourth aspect of the invention to attain the above object, there is provided a seat belt system including the seat belt buckle engagement detector as stated in the first aspect.
Since the present seat belt system includes the seat belt buckle engagement detector as stated in the first aspect, the engagement of the buckle and the tongue plate of the seat belt can be detected even in case the engagement can not be detected in the conventional seat belt buckle engagement detector to thereby carry out predetermined operations of the system.
According to a fifth aspect of the invention to attain the above object, in the fourth aspect, there is provided a seat belt system having a function for displaying a warning showing that the buckle and the tongue plate of the seat belt are not engaged with each other.
Since the seat belt system of the present aspect has the function for displaying the warning showing that the buckle and the tongue plate of the seat belt are not engaged with each other even if the ignition switch of the automobile is turned off, the seat belt system can provide a warning for putting on the seat belt even in case the automobile is driven by hauling. Also, the seat belt system can provide a warning to put on the seat belt even before a passenger gets on the automobile and turns on the ignition switch.